1. Field of the Invention
The present invention relates to an X-ray examination apparatus and an X-ray examination method using the same.
2. Description of the Related Art
Recently, with high integration of an LSI (Large-Scale Integration) by submicron microfabrication technique, functions which were divided into a plurality of packages in the prior art can now be integrated into one LSI. Since increase in the number of pins that arise as a result of incorporating the functions necessary for one package cannot be responded with the conventional QFP (Quad Flat Package) and PGA (Pin Grid Array), LSI of BGA (Ball Grid Array) and CSP (Chip Size Package) package, in particular, is recently being used. The BGA package is used where ultraminiaturization is necessary such as a portable telephone even if the required number of pins is not great.
The BGA and CSP package of the LSI greatly contribute to ultraminiaturization, but has a feature in that the solder portion etc. cannot be seen from the outer appearance after assembly. When inspecting a print substrate etc. mounted with the BGA or CSP package, the quality determination is performed by analyzing a transmissive image obtained by irradiating an X-ray onto an examining object. For instance, patent document 1 (refer to, for example, Japanese Patent Application Laid-Open Publication No. 2000-46760) discloses an X-ray sectional examination apparatus capable of obtaining a clear X-ray image by using an X-ray planar sensor to detect the transmissive X-ray.
In such an X-ray examination apparatus, the X-ray is emitted by impinging the electron beam onto a target such as tungsten. When the electron beam impinges the target, the target is damaged. Thus, the target deteriorates if the electron beam is impinged on the same position of the target for greater than or equal to a predetermined time.
The X-ray source of the X-ray examination apparatus includes a method in which a position of impinging the electron beam onto the target is fixed (fixed focus method), and a method in which the electron beam is repeatedly impinged onto a predetermined position in a discrete manner. Longer lifespan can be expected in the latter method than in the fixed focus method but the target similarly deteriorates.
When the target deteriorates, maintenance of the target needs to be carried out as the irradiated X-ray amount decreases and the X-ray image becomes dark, or the image quality lowers and the examination efficiency degrades. The deterioration of the target is limited to a small portion where the electron beam impinges, and thus the user performs the maintenance of the target by rotating the target surface. The position where the electron beam impinges shifts from the deteriorated position, and characteristics similar to a new target can be obtained.
For instance, when performing the X-ray examination using Micro-focus X-ray source L9191 manufactured by Hamamatsu Photonics K. K., the user carries out the maintenance of the target by manually rotating the target surface.
Generally, the lifetime of the target of the transmissive X-ray source is between about 300 hours to 500 hours. If the frequency of use is small as with an analyzer, the period until the target deteriorates is long and the trouble necessary for carrying out the maintenance of the target will not be a problem. However, if operated for a long period of time as with an in-line examination apparatus, the period until the target deteriorates is short, and thus it is important that the maintenance of the target is easy and convenient to carry out.
In a method of carrying out the maintenance by manually rotating the target, the maintenance workman needs to be familiar with the task and the task requires time. Information for maintenance, for example, how long and at which position of the target the X-ray is irradiated need to be managed.
In the method of repeatedly using a predetermined position of the target in a discrete manner in the scanning X-ray source, the electron beam is impinged on a plurality of positions, and thus the amount of information for maintenance becomes enormous, and becomes difficult for the user to manage.